The present invention generally relates to laser diode packages, and more particularly to a laser diode package using a passive microscale liquid-vapor phase change heat pipe.
High powered laser diodes for a variety of applications require very large heat flux removal (>400 W/cm2). To date, most solutions have relied upon microchannel cooling technology, but no solution has been verified at very large diode powers (e.g., >200 W/bar). Using an embedded heat pipe significantly reduces thermal resistance, and it may be possible to decrease the thickness of the heat pipe further to increase brightness. However, the multi-phase heat transfer and fluid flow characteristics at the scales required for effective heat removal is poorly understood.
Heat removal from laser diodes to the ultimate cooling fluid is the fundamental limitation for state-of-the-art laser diode systems. Heat generated at the surface of the diode must be transported through a variety of intervening thermal to the ultimate cooling fluid. This heat is conducted along extended surfaces, which impose thermal gradients onto the surface of the diode, thus limiting their lifetime and performance. In state-of-the-art systems, the team has observed that heat is conducted from more insulated diodes to neighborfsing diodes, which undesirably broadens the emitted wavelength spectrum. Furthermore, the sensible heat rejected to the cooling fluid also impacts the temperature uniformity of the system.
Increasing the power output per diode chip increases pump brightness, facilitating pump coupling to the laser gain medium, and decreases system cost on a per-Watt basis. Semiconductor light emitting diodes (LEDs) have similar technical issues as laser diodes, and solid state LED lighting is a targeted area for high-efficiency, general illumination laser diode products through the advancement of semiconductor technologies. High-brightness LEDs offer up to 66% savings in electric power consumption over conventional lighting and lead to a predicted $60B market in the next decade. However realizing these efficiencies requires highly efficient waste heat removal from the LED device and package.